Biomedical subjects

R B Boyd

Publications and source records attributed to R B Boyd.

12 recordsLinked to original sources

PubMed1996

Alterations in glomerular permeability in streptozotocin-induced diabetic rats.

The alteration in glomerular basement membrane permeability associated with microangiopathy in streptozotocin-induced diabetic rats was studied by determining the movement across the glomerular basement membrane of anionic ferritin probes injected into rats at different points in the development of the disease. Visualization of the concentration gradient of anionic ferritin and changes in ultrastructure was accomplished by electron microscopic examination of renal tissue prepared from both control and diabetic rats. In all control rats, the anionic ferritin did not leave the glomerular capillary lumen, nor were there any changes in the normal morphology of the glomerular capillary wall. In the diabetic animals, the concentration of anionic ferritin shifted from the capillary lumen in the abluminal direction. Distinct morphologic changes, such as widening of endothelial intercellular junctions, focal detachment of podocyte foot processes, and extensive thickening of the glomerular basement membrane, were noted in the diabetic rat, and these changes appear to correlate with the observed increase in permselectivity of anionic ferritin across the glomerular capillary wall.

Animals↗

PubMed1991

Quantifying magnification in pedal radiographs.

Morphometric comparison between metatarsals on pedal radiographs and preserved bone specimens provides a method to quantify the amount of magnification imparted on a radiographic image. Conversion factors are presented for dorsoplantar and lateral projection images, which are of value in the preoperative assessment of patients. Factors that influence radiographic quality are discussed, with an emphasis on the geometry of projecting an accurate image.

Humans↗

PubMed1991

Electron microscopy of changes in lower extremity muscles in Duchenne muscular dystrophy.

Duchenne muscular dystrophy is a genetic disease with a sex-linked pattern of inheritance. This disease is present at birth, becomes symptomatic during early childhood, leads to inability to walk near the end of the first decade, and usually results in death by the end of the second decade. In this study, the extensor digitorum longus and soleus muscles from genetically dystrophic mice were examined at the electron microscopic level. The authors describe their results and discuss how these findings might provide some insight into one of the mechanisms of fiber necrosis in Duchenne muscular dystrophy.

Animals↗

PubMed1990

Significance of capillary basement membrane changes in diabetes mellitus.

Diabetes mellitus is a disease in which the capillary basement membranes are substantially altered. This diabetic microangiopathy is characterized by a thickening of the basement membrane and changes in its permeability characteristic due to a disturbance in the production and distribution of its functional components. Glucose metabolism and insulin imbalance have been implicated in these basement membrane modifications. The authors describe normal capillary basement membrane architecture and then discuss how pathologic changes caused by diabetes mellitus are related to diabetic foot pathology.

Basement Membrane↗

PubMed1986

A comparison of anionic sites in the glomerular basement membranes from different classes of fishes.

Cationized ferritin was injected into the circulatory system of teleosts, the sea raven and Atlantic eelpout, and into elasmobranchs, the spiny dogfish and the skate, to determine if the glomerular basement membranes (GBM) from these different groups of fishes possess anionic binding sites similar to those present in the GBM of mammals. The distribution of cationized ferritin was the same in all fishes listed. Cationized ferritin was localized only in the GBM and the mesangial matrix. The regular distribution of cationized ferritin within the laminae rarae (approximately 60 nm intervals) was taken as evidence of the presence of anionic binding sites. Cationized ferritin did not bind to the glomerular capillary endothelium, nor was any of it localized at the base of the slit diaphragms of the foot processes of the podocytes. The distribution of binding sites in the GBM of these fishes is similar to that in another teleost, the winter flounder, and in a cyclostome, the hagfish.

Animals↗

PubMed1986

Teicoplanin as a prophylactic antibiotic for dental bacteraemia.

The potential of teicoplanin, a new glycopeptide antibiotic, was assessed according to its ability to decrease the occurrence and severity of bacteraemia following dental extraction. Preliminary studies with ten volunteers showed that mean peak serum concentrations of teicoplanin were reached 3 hours after intramuscular administration and were 2.6 mg/l (1.5 mg/kg regimen) and 5.0 mg/l (3 mg/kg regimen). Three groups of ten patients participated in the bacteraemia study. Group one received no prophylaxis whereas groups two and three received 200 mg of teicoplanin intramuscularly, or 3 g amoxycillin orally respectively, 1 h prior to extraction. Sequential blood cultures were inoculated at timed intervals from a single venous blood sample taken 2 min after commencing surgery. Bacteraemia was detectable in all patients who received no prophylaxis whereas those given teicoplanin and amoxycillin had detectable bacteraemia in 6/10 and 4/10 cases, respectively. Teicoplanin was clearly effective in reducing the incidence and degree of post dental extraction bacteraemia although apparently rather less so than amoxycillin. In-vitro tests of susceptibility and bactericidal activity showed that teicoplanin possesses comparable activity to those antibiotics which are either in use or have been used for the suppression of bacteraemia following dental extraction.

Adult↗

PubMed1984

Glycosaminoglycan biosynthesis in the isolated perfused rat lung.

The suitability of an isolated lung, perfused under carefully monitored conditions, for the study of the biosynthesis of glycosaminoglycans was examined for the rat lung using either [35S]-sulfate or [6-3H]glucosamine. Metabolic and electron-microscopic studies after 3 h of perfusion showed that under the conditions of this study the isolated lung showed no anatomical or metabolic derangements. All glycosaminoglycans normally synthesized in the intact lung were identified. The predominant glycosaminoglycan was heparan sulfate (40% of total). Approximately 14% of the glucosamine incorporated into the glycosaminoglycans was found in hyaluronic acid. Less than 5% of either label was in heparin. The remainder of the synthesized glycosaminoglycans, with the exception of 10% which could not be identified, consisted of the chondroitin sulfates and dermatan sulfate. The relative proportions of the newly synthesized glycosaminoglycans, including the low amounts of heparin, are similar to those found in isolation of endogenous lung glycosaminoglycans. The isolated perfused rat lung appears to be a useful model for the study of glycosaminoglycan biosynthesis by the intact lung.

Animals↗

PubMed1983

The seasonal distribution of anionic binding sites in the basement membrane of the kidney glomerulus of the winter flounder Pseudopleuronectes americanus.

The blood of the winter flounder, Pseudopleuronectes americanus, contains small (3000-8000 daltons) anionic peptides (pI less than 5) with antifreeze properties. They are present only in the winter and are retained in the circulatory system even though inulin and polyethylene glycol, of comparable molecular size, are filtered by the glomerular kidney. Electron micrographs of flounder-kidney glomeruli revealed that their structure is similar to that of mammals and that cationized ferritin binds at regular 60 nm intervals in the lamina rara interna of the basement membrane as it does in mammals. The binding of cationized ferritin, in conjunction with the previous observation that cationized antifreeze peptides exhibit a marked increase in renal clearance, suggests that an anionic repulsion barrier within the glomerular basement membrane of the winter flounder is responsible for the conservation of the anionic antifreeze peptide molecules found in their blood during the winter. This barrier also appears to be present in summer specimens of the flounder which lack the antifreeze peptide.

Animals↗

PubMed1980

The secondary lamellae of the gills of cold water (high latitude) teleosts. A comparative light and electron microscopic study.

The fine structure of the secondary lamellae of gills was examined in two cold-water marine teleosts, the winter flounder, Pseudopleuronectes americanus, and the antarctic cod, Trematomus borchgrevinik. In both species the overall lamellar fine structure is similar to that of other marine teleosts. The major variations in cellular organization involve the distribution of both the "chloride cells" and the mucous cells on the secondary lamellae of P. americanus. At winter water temperatures of +2.5 degrees C, significantly more chloride and mucous cells are present than in summer with water temperatures of +15.2 degrees C. Both cell types are routinely present throughout the length of a secondary lamella as far as the lamellar tip. The chloride cells on the secondary lamellae are always situated in the inner layer of epithelium deep to the outer pavement cells. T. borchgrevinki shows no apparent difference in the distribution of mucous cells either at its normal water temperature of -1.9 degrees C or at a temperature of +4 degrees C, the upper limit of its thermal tolerance to which some specimens were adapted in the aquarium. Chloride cells were never observed on the secondary lamellae of T. borchgrevinki. This suggests that low environmental water temperatures may be related to the distribution of mucous cells and chloride cells on the secondary lamella of the teleost gill.

Animals↗

PubMed1979

Renal conservation of antifreeze peptide in Antarctic eelpout, Rhigophila dearborni.

In Antarctic notothenioid fishes large amounts (3% w/v) of small molecular weights of 2,600-23,500 and would be expected to be filtered into the urine, they remain in the blood because the kidneys of these fishes contain only aglomerular nephrons. Unlike the situation in most fishes, urine formation is the result of secretion rather than filtration and reabsorption. On the other hand, the peptide antifreezes in Northern Hemisphere fishes such as the winter flounder. Pseudopleuronectes americanus, are retained by the glomerular kidney even though inulin, of comparable weight, is rapidly filtered from the blood into the urine. The Antarctic eelpout (zoarcid), Rhigophila dearborni, which is unrelated to either the Antarctic notothenioids or P. americanus, also uses a peptide antifreeze (molecular weight 6,000) which is maintained at a concentration of 3% (w/v) in the blood plasma. We report here that the lack of antifreeze in the urine of R. dearborni probably reflects the fact that the glomeruli are not functional and cannot filter. We support this conclusion with morphological and physiological evidence and relate our findings to the conservation of biological antifreeze necessary for life in ice-laden polar waters.

Adaptation, Biological↗

PubMed1977

Resistant ventricular tachycardias and recurrent cardiac arrests. 96 episodes.

A 66-year-old man suffered an acute myocardial infarction complicated by multiple episodes of ventricular tachycardia and 96 episodes of ventricular fibrillation requiring cardioversion over a period of 55 days. Following ventricular aneurysmectomy, the ventricular tachycardia persisted. This converted to regular sinus rhythm with a regimen of disopyramide phosphate, quinidine, and propranolol.

Aged↗

PubMed1975

A gross and microscopic study of the respiratory anatomy of the Antarctic Weddell seal, Leptonychotes weddelli.

Four species of Phocidae, or true seals, inhabit the waters surrounding the Antarctic continent. These animals are thought to have different diving capabilities. The Weddell seal, Leptonychotes weddelli, is known to be capable of attaining depths up to 600 meters. The respiratiory system of the Weddell seal shows the usual adaptations to an aquatic environment characteristic of other marine. These include lungs that undergo compression acollapse at depths greater than 70 meters; hyaline cartilage in the tracheo-bronchial tree as far as the terminal bronchioles; and large amounts of smooth muscle surrounding the distal-most bronchioles. The collapsible lungs provide a mechanism by which air is forced from the alveoli adjacent to the pulmonary capillary beds thereby preventing the absorption of nitrogen gas into the bloodsteam. The presence of hyaline cartilage throughout most of the tracheo-bronchial tree increases the effective dead air space that accommodates most of the air forced from the collapsed lungs. The smooth muscle surrounding the respiratory bronchioles prevents their collapse while under the pressures of a deep dive. Collapse of the respiratory bronchioles not supported by cartilage would trap air in the lung alveoli during a dive. In addition, large- sac-like "diverticulae" are found in the submucosa throughout the tracheo-bronchial tree. These diverticulae, which open directly into the lumen of the tree, appear to be modified glands whose cells, in most cases, do not appear to be specialized for secretory function. They are most numerous in the more distal bronchi and terminal bronchioles where they are situated on both the luminal and adventitial sides of the hyaline cartilage supporting the walls of the air passages. Diverticulae are not found in the respiratory bronchioles or in the respiratory portion of the lungs.

Acclimatization↗